The invention relates to devices for monitoring subsurface temperatures.
Agricultural diversions can result in significant uses of surface water. Estimating seepage has many practical challenges such as accuracy of inflow-outflow measurements due to non-steady flow conditions. The use of heat as a tracer to estimate seepage losses has been demonstrated in the literature, but the availability of distributed temperature probes is largely unavailable for this purpose.
Measuring temperature beneath streambeds has typically been performed using temperature sensors that are attached to a cable and hung inside a pipe such as a well or piezometer (Hatch et al., 2006). However, the exposed pipe driven into an active river or stream has a high risk of damage due to high velocities and debris (branches, algae, trash), and access to the data requires removal of the sensors, connection of each sensor to a portable computer, and then return of the sensors following data retrieval. This process disrupts the experiment and is prone to errors caused by shifting of sensors. Removal of erroneous temperature data that reflects the time the sensors were exposed to ambient air temperatures is necessary using this method.
Thermistor wires that are connected to a data logger have been used to measure sediment temperatures (Bartolino and Niswonger, 1999). Thermistor wires subjected to high stage or velocities are subject to damage from canal debris and such placements are often destroyed at high flow conditions. Further, this type of system requires the use of an external insulated housing to store the data logger, battery, and reference thermistor to correct field data due to reference-junction errors (Stonestrom and Blasch, 2003). The expense of the data logger due to batteries and required maintenance, and limited locations where this system can be deployed without damage prohibit wide applications of this approach.
Thus, an improved temperature probe is needed.